Maybe you weren't hacked.
Try the following
Start up in Safe Mode
Steps 1 through 7
Also try restoring from your Time Machine backup if this does not help.
If these fail make an appointment at an Apple store and visit their Genius bar.
I use Sophos as my anti-virus software but there are many others that are as good or better.
Check your service options with a serial number: https://getsupport.apple.com/ProductSelector.action
Click on Take it in for service
Then click on View & edit details
This will show you your exact model and show the support options you have for your Apple product.
It's extremely unlikely that you have been hacked or infected with malware. My first guess would be a badly corrupt, and possibly dying, hard drive. Do you have backups? If not, you're about to learn the hard way why they're important. You will probably need to try file recovery to get back the contents of your Documents folder. See:
First, though, just check to make sure you're looking in the right place. In the Finder, choose Go -> Documents. Is the window that opens empty, or are your files in it?